Coaxial cable television systems have been in widespread use for many years and extensive networks have been developed. The extensive and complex networks are often difficult for a cable operator to manage and monitor. A typical cable network generally contains a headend which is usually connected to several nodes which provide content to a cable modem termination system (CMTS) containing several receivers, each receiver connects to several modems of many subscribers, e.g., a single receiver may be connected to hundreds of modems. In many instances several nodes may serve a particular area of a town or city.
The hybrid fiber coaxial (HFC) network and CATV market is driving toward highest density transport as well as having flexible capability to transmit QAM signal in a cost effective matter. Multi transmitters, such as quadrature amplitude modulation (QAM) & dense and coarse wavelength division multiplexed (DWDM) & (CWDM) CATV transmitters, are gathered next to each other. Each transmitter typically transmits at a specific single wavelength channel of the DWDM, e.g., up to 40 wavelengths on the ITU grid with a 100 Ghz (0.8 nm) spacing. All these wavelengths typically are combined on a single fiber in order to increase fiber usage and reduce cost.
The typical analog CATV optical transmitter is constructed as a single module or circuit board. Each module generally contains a single wavelength laser which provides one channel, and as many as 40 channels (e.g. 40 transmitter boards) are provided in a headend unit. A cable operator generally needs to maintain an extra board for each channel to replace a transmitter board when it becomes defective or to simply change the channel parameters, such as transmission frequency. The transmitter boards are bulky and expensive, and are often individually built and tuned. Accordingly, what is needed is a small form factor pluggable optical CATV transmitter which takes up much less space, can be easily replaced, and is cost effective. Furthermore, with the increasing demand for more data bandwidth to be available to subscribers, many HFC networks are attempting to provide more bandwidth by pushing the optical fiber deeper into the network to bring the point at which the optical communications are converted to RF communications over a coaxial cable closer to the end user. Therefore new cost effective platforms of optical transmitters are needed to transmit data from remotely located end user subscribers and/or nodes back to the head end unit and vise versa.